1. Field of the Invention
This invention relates to printer devices, and more particularly to an improved printer device of a type, in which a hammer mechanism for printingly impacting a type drum by means of hammer springs is provided and hammers are held in retracted states for respective types by means of a reset cam against the resiliency of the hammer springs.
2. Description of the Prior Art
There have heretofore been well known printers of various types as output devices for data processing units or electronic calculators. As a compact printer, a flying printer is preferable in which hammers are printingly driven onto a type drum provided on the outer periphery thereof with a plurality of types at desirable printing timings. The flying printer can carry out a clear printing operation by the use of an ink ribbon or an ink roll. Normally, the printing onto the type drum is performed through the resiliency of the hammer springs, and a reset cam is used for separating the hammer from the type drum after the printing and resetting the hammers in a retracting state against the resiliency of the hammer springs. It has been known that the reset cam is rotated in synchronism with the type drum or in accordance with a desired printing cycle, whereby the reset cam repeats mechanical contact with the hammers during printing operation of the printer.
In the conventional printers, the aforesaid contacts between the reset cam and the hammers should necessarily be repeated in the respective reset portions, and hence, there have been presented such various disadvantages that the wear due to sliding contact between the reset portion and the hammers and the power consumption caused by the contacting resistance are increased and noise is caused by the impingements and contact between the reset cam and the hammers. Particularly, in compact printers, there have been presented various disadvantages of decreased durability of the printer and of necessity of the provision of a noise cover.
As the improved conventional printer device, there has been proposed a device disclosed in Japanese Patent Laid-Open (Kokai) No. 128575/82, according to which, a retracting cam is provided which turns the hammer to a retracted position out of contact with the reset cam in each printing cycle and, in a hammer holding member, a second holding portion for holding the hammer in the retracted position is provided in addition to a first holding portion for holding the hammer at the retracted state.
In consequence, in the conventional printer device of the type described, the hammer, which has been temporarily turned to the retracted position, is not brought into contact with the reset arm before being used for the succeeding printing action, so that there have been achieved remarkable improvements in reducing the torque loss, noises and so forth.
However, in this device, there has been presented such a disadvantage that, in order to hold the hammer at least at two holding positions including the first retracted position and the second retracted position, a long moving stroke is required of the hammer holding member. Normally, the hammer holding member is of such an arrangement that an armature to be attracted by an electromagnetic solenoid is used, the hammer is held at either one of positions by the armature in non-excited conditions, and an excitation signal or printing signal is fed to the electromagnetic solenoid at a desirable timing to attract the armature instantaneously, whereby the resultant unlatching operation drives the hammers. In consequence, there have been presented such drawbacks that the long moving stroke required of the armature weakens the attracting force of the solenoid, particularly an initial attracting force, whereby a high excitation current is required for compensating for the weakened attracting force and, the electromagnetic means need to be large-sized.